If Johnston could come to Pemberton's relief or if Pemberton could break through and unite with Johnston, they could together save Vicksburg. But Grant had resolved that they should not join forces, and to the problem confronting him he devoted himself body and mind. Constantly in the saddle, watching every detail of the work as the attacking army slowly dug its way toward the city and personally posting the troops holding Johnston at bay, his quiet, determined face and mud-splashed uniform became familiar sights to the soldiers, and his appearance on the lines was invariably greeted with inspiring cheers. By July, the trenches of the besieged and the besiegers were so close together that the opposing pickets could take to each other, and the gun-boats threw shells night and day into the town. Still Pemberton would not surrender and many of the inhabitants of Vicksburg were forced to leave their houses and dig caves in the cliffs upon which the city was built to protect themselves and their families from the iron hail. It was only when food of every kind had been practically exhausted and his garrison was threatened with starvation that Pemberton yielded. On July 3, 1863, however, he realized that the end had come and raised the white flag. Nearly twenty-four hours passed before the terms of surrender were agreed upon, but Grant, who had served in the same division with Pemberton in the Mexican War, was not inclined to exact humiliating conditions upon his old acquaintance whose men had made such a long and gallant fight. He, accordingly, offered to free all the prisoners upon their signing a written promise not to take arms again unless properly exchanged, and to allow all the officers to retain their side arms and horses. These generous terms were finally accepted, and on July 4, 1863, the Confederate army, numbering about 30,000, marched out in the presence of their opponents and stacked their arms, receiving the tribute of absolute silence from the 75,000 men who watched them from the Union ranks. Four months before this event, Halleck, the Commander-in-Chief, had advised Grant and other officers of his rank that there was a major generalship in the Regular Army for the man who should first win a decisive victory in the field. The captor of Vicksburg had certainly earned this promotion, for with its fall the Mississippi River was controlled by the Union and, in the words of Lincoln, "The Father of Waters again ran unvexed to the sea." Chapter XXII. -- The Battle of Gettysburg